CVE-2026-50721: IKEv1 Denial of Service via RSA-SHA1 (PKCS#1 Version 1.5 Encrypted) authentication payload

CSIRTS triage

What

This vulnerability allows for a Denial of Service via RSA-SHA1 authentication payload.

Who is affected

Systems utilizing IKEv1 are affected.

Urgency

High urgency for remediation due to a CVSS score of 8.1 indicating significant risk.

Action

Apply patches or mitigations as soon as they are available.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source

Microsoft Security Response Center (INTL · vendor-psirt · site)

Severity

high — CVSS 8.1

Published

2026-07-02

Exploitation

Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50721

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

• Low exploitation riskCVE-2026-507210.39% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 31% of all scored CVEs.

Referenced CVEs

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

• unknownMultiple vulnerabilities in Microsoft Azure Linux (July 10, 2026)cert-fr-avis
• highCVE-2026-50721: Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verif…nvd

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